I had such an experience. In the past, I often
went to bed very late at night. So I felt very tired and
sleepy the next day. I couldn't pay attention to what
my teachers said, so I couldn't learn well. Later, my
mother asked me to go to bed before 10 o'clock.
Gradually, I have developed this habit. Now I feel
much better. I can follow my teachers in class and
learn well.